Extraordinary Case ReportCutaneous Mastocytosis With Predominant Infiltration of PromastocytesKnöpfel, Nicole MD*; Colmenero, Isabel MD†; Matito, Almudena MD, PhD‡; Latour, Irene MD*; Noguera-Morel, Lucero MD*; Hernández-Martín, Angela MD*; Alvarez-Twose, Iván MD, PhD‡; Torrelo, Antonio MD*Author Information Departments of *Dermatology, and †Pathology, Hospital Infantil Universitario Niño Jesús, Madrid, Spain; and ‡Instituto de Estudios de Mastocitosis de Castilla La Mancha (CLMast), Hospital Virgen del Valle, Toledo, Spain. Correspondence: Nicole Knöpfel, MD, Department of Dermatology, Hospital Infantil Universitario Niño Jesús, C/Menéndez Pelayo, 65, Madrid 28009, Spain (e-mail: firstname.lastname@example.org). The authors declare no conflicts of interest. The American Journal of Dermatopathology: April 2019 - Volume 41 - Issue 4 - p 296-299 doi: 10.1097/DAD.0000000000001246 Buy Metrics Abstract Mastocytosis is a heterogeneous group of disorders with a variable clinical course, ranging from indolent disease with normal life expectancy to highly aggressive disease. In the skin, mast cells may show a spindle-shape appearance or appear as round cells with wide, polygonal cytoplasm. In this study, we present a case series of 4 patients with cutaneous childhood-onset mastocytosis in whom skin mast cells showed striking nuclear pleomorphism with bilobed and multilobed nuclei. Such finding does not seem to represent a malignant phenotype of the disease in the skin, although the true biological significance and the potential prognostic impact remain to be determined. Copyright © 2018 Wolters Kluwer Health, Inc. All rights reserved.